Chair base



FIG. 1 is a front perspective view of the chair base in accordance withthe present invention;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is another perspective view thereof showing a chair in brokenline.

The portions of the design shown in broken line are present forillustrative purposes only and form no part of the claimed design.

The ornamental design for chair base, as shown and described.